Biopreservation of brycinus nurse fish (Onangananga) using beeswax and thyme essential oil with complementary packaging

Abstract

Bio-coatings maintain food quality by minimizing exchange of oxygen, light and moisture across the food matrix, hence inhibiting microbial proliferation. Including essential oils in the bio-coatings enhances flavor, antioxidant and antimicrobial properties thereby extending shelf life. This study aimed to evaluate the preservation effectiveness of beeswax and thyme essential oil coatings on sun-dried Brycinus nurse fish (Onangnanga) obtained from Panyimur market, Pakwach district, Uganda. Sun-dried B.nurse samples were stored under ambient conditions in open (box), vacuum, and container packaging for six weeks. Analyses were conducted weekly to assess microbial quality (Salmonella, Pseudomonas, E. coli, Staphylococcus, and total plate counts (TPC)) and, biochemical properties (pH, moisture content, total volatile basic nitrogen (TVBN), and Thiobarbituric acid reactive substances (TBARS)). Sun-dried B.nurse exhibited low microbial quality with TPC of 7 log CFU/g, detectable levels of Salmonella spp, E.coli spp. ranged from 3.56 to 3.74 log CFU/g and Staphylococcus spp from 1.11 to 6.9 log CFU/g. Moisture content significantly (p < 0.05) increased from 15.06% during storage as follows: Container packaging to 28.81%, vacuum package to 16.26%, beeswax coating to 26.1% and thyme with beeswax coating to 21.80%. TVBN levels significantly increased (p< 0.05) from 24.12 mgN/100g to 35.61 mgN/100g, with the different treatments as follows: container packaging (34.39 mgN/100g), vacuum packaging (35.61 mgN/100g) beeswax coating (32.08 mgN/100g) and thyme with beeswax coating (30.83 mgN/100g). TBARS values increased significantly (p<0.05) from 4.03 mgMDA/kg to 18.25 mgMDA/kg, with container packaging (11.81 mgMDA/kg), vacuum packaging (15.14 mgMDA/kg), beeswax coating (12.46 mgMDA/kg) and thyme with beeswax coating (9.92 mgMDA/kg). The pH values remained stable regardless. Both packaging types and coatings significantly (p<0.05) influenced the quality of sun-dried B. nurse. This study showed that beeswax and thyme essential oil coatings combined with suitable packaging preserved the quality of sun-dried Brycinus nurse , hence effectively extending its shelf life by 21 days.